In warm weather, inadequate ventilation will trap hot air in the attic, causing air c onditioning systems to work harder, or leaving your home's interior hotter and less comfortable. Attic Ventilation: In both hot and cold weather, insufficient attic ventilation may cause moisture in the attic to become trapped and condense on the rafters. This condensed moisture can drip down onto the insulation and reduce its effectiveness.
Excessive energy costs can result.